The a steam generator and a method of burning fuels in a steam generator of the same type.
A steam generator of this type is outstanding for its brief startup and shutdown times, low pollutant output, good consumption, and potential for burning any type of fuel. It cannot, however, be built above a certain size at a justifiable cost.
That the output of a fluidized-bed combustion chamber can be increased by pressurizing it is known. Known fluidized-bed combustion chambers operate with a strictly stationary fluidized bed and without ash feedback. The combustion chamber of the steam generator and its cyclone is surrounded by a pressure housing. Since the steam generator is one component of a combination gas-and-steam power plant, the flue gases are extracted at processing pressure and at a temperature of 850.degree. C. and supplied to a gas turbine. A cogeneration plant of this type both requires expensive high-temperature pressurized hot-gas filtration and involves hot surfaces inside the fluidized bed and hence exposed to erosion. At an incoming-gas temperature of 850.degree. C., corrosive constituents of the flue gas can damage the gas turbine. Finally, the shipping and storage of bed material makes stoking relatively expensive.
A pressurized steam generator with a circulating fluidized-bed combustion chamber is also known. The combustor, cyclone, and steam-generator convection section in this steam generator are all accommodated in separate pressurized vessels. Processing technology also demands flow-bed coolers to cool the circulating solids.